1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus suited for use as a copying machine, a printer (such as LED printer and laser beam printer), a facsimile machine, a word processor, and the like that are configured to form an image on a recording medium by using an electrophotographic image forming process.
2. Description of the Related Art
Hitherto, in image forming apparatus using an electrophotographic image forming process, there has been known a process cartridge system in which photosensitive drums and developing units each housing a developing roller to affect the corresponding photosensitive drums and each containing developer (toner) to be used for image formation are integrated with each other. Further, there has also been known a developing cartridge system in which the cartridge has only the developing units independently of the photosensitive drums.
Those cartridge systems allow users themselves to perform maintenance of the apparatus without service engineers. Thus, those cartridge systems have been widely used in electrophotographic image forming apparatus.
Further, there has also been known a technology of arranging a moving member to which those cartridges are mounted and being removable by being pulled out from an inside of a main body of the image forming apparatus to a predetermined position so that an operation of replacing the cartridges can be performed. The technology allows users to easily replace cartridges containing the developer (Japanese Patent Application Laid-Open No. 2009-157135).
However, in the image forming apparatus using the above-mentioned related-art moving member to which the cartridges are mounted, a problem of instability of positioning image bearing members with respect to transfer devices in the main body, or a problem of a large mounting load to be applied when the moving member is mounted into the main body has not yet been solved.
In other words, there have been demands to reduce the instability of positioning the image bearing members with respect to the transfer devices in the main body, or to reduce the large mounting load to be applied when the moving member is mounted into the main body.